Generally, organic sulfonic acid compounds are used for acid catalysts, ion exchange membranes, etc., in synthetic reactions because of their high acidity, and the salts of organic sulfonic acid compounds have a wide range of uses such as cell electrolytes, photo acid generators in resist materials, photosensitized solar cells, capacitors, solvents, etc. In particular, sulfonic acid compounds wherein the carbon in the α-position to a sulfonic acid group is substituted with fluorine have extremely high acidity and exhibit interesting characteristics.
For example, fluorosulfonic acids represented by formula (A):R0—CF2—SO3H  (A)are used as acid catalysts, etc., because of their high acidity, and salts thereof are used as cell electrolytes, etc. Specifically, such compounds that have been reported include:
compounds wherein R0 is a fluorine atom or a fluoroalkyl group; compounds wherein R0 is an aryl group (see J. Org. Chem., 1998, 63, 8052-8057 and Tetrahedron Letters, 1999, 40, 4149-4152); compounds wherein R0 is a cyano group (see Japanese Unexamined Patent Publication No. 2002-3466); compounds wherein R0 is a carboxyl group, an ester group, or a carbamoyl group (see Ukr. Khim. Zh. (Russ. Ed.), 1986, 52(4), 405-6; Izv. Akad. Nauk SSSR, Ser. Khim., 1968, 7, 1565-70; and Izv. Akad. Nauk SSSR, Ser. Khim., 1967, 6, 1289-94); compounds wherein R0 is an acyl group (see Zh. Org. Khim., 1975, 11(8), 1604-7); compounds wherein R0 is a sulfonic acid group, a salt thereof, or a sulfonamide group (see J. Electrochem. Society, 1985, 132(10), 2424-6 and Z. Naturforsch., B: Chemical Sci., 1998, 53(2), 135-144); compounds wherein R0 is —SF5 (see Inorg. Chem., 1990, 29(22), 4588-90); etc. These fluorosulfonic acids are organic acids having high acidity.
The application of high-acidity fluorosulfonic acids and derivatives thereof is expected not only in the above-mentioned uses but in a wide range of fields in which the characteristic properties thereof can be put to use. Therefore, a stable organic fluorosulfonic acid is strongly desired that has even higher acidity than the above-mentioned known fluorosulfonic acids and that easily allows various derivatives to be synthesized therefrom.
In addition, J. Fluorine Chem., 1994, 67, 27-31 reports fluorosulfonyl fluorides such as CF3SO2CF2SO2F, FSO2CF2SO2CF2SO2F, CF3SO2CF2SO2CF2SO2F, etc.